This invention relates to an intake system for engines and more particularly to an improved high efficiency intake system for an engine that permits maximum power output to be achieved with good running under mid and low range conditions.
In order to offset the disadvantages of engines having only a single induction passage serving each combustion chamber and the compromises dictated thereby, it has been proposed to provide an induction system for an internal combustion engine wherein each combustion chamber is served by a plurality of induction passages. In order to improve the running under partial loads, it has been the practice to provide a throttle valve in one of the induction passages. This throttle valve is operated so that it remains closed during a substantial portion of the engine running and opens only at the high end of the engine power curve. Such devices provide generally good running at high outputs and at low outputs. However, it has been noticed that the performance of engines having such dual induction systems with separate throttle controls at part throttle and part load is less than satisfactory. That is, it has been found that this type of induction system results in a torque curve for the engine that has a flat spot or, even worse, a valley in the torque curve at mid range running.
The inventors have discovered that a reason for this unfavorable performance phenomena is that the area of the induction passage in which the throttle valve is positioned functions as a side branch resonance chamber during the running conditions when the throttle valve is closed. Thus, even though there is no or substantially little air flow through this particular induction passage, during certain engine running conditions, the resonance chamber adversely affects the induction into the combustion chamber through the primary intake passage. As a result, the induction efficiency of the engine under this running condition is poor and the part range performance suffers.
It is, therefore, a principal object of this invention to provide an induction system for an internal combustion engine in which high power outputs are possible and in which part range running performance is significantly improved.
It is a further object of this invention to provide a high efficiency induction system for an internal combustion engine.
It is a further object of this invention to provide an induction system for an internal combustion engine of the type including plural intake passages serving each combustion chamber of the engine and wherein induction system resonance is avoided.